In restorative dentistry, it is usual after the application of a filling to produce the desired shape and surface structure thereof in several steps, starting from the coarse working of the anatomic shape by means of diamond cutters up to the polishing of the filling surface. This process involves many instrument changes as instruments of different grain are required between the coarse shaping and the polishing operation.
Another problem is the fact that the surfaces of teeth have complex shapes and the usual polishing instruments only poorly adapt to the fissured surfaces, so that the instruments must be carefully guided in order to reach all portions that have to be polished.
An important improvement in this respect has been attained by the use of brushes whose bristles are coated with abrasive particles. These brushes allow one to polish the filling in a single step directly after the coarse shaping by means of diamond cutters. Furthermore, highly edged and angular structures can be reached without a special guidance of the instrument.
However, these brushes exhibit a number of serious drawbacks which are mainly due to the fact that the bristles, on account of the abrasive particles, are relatively thick:
1. They are stiff and unwieldy; PA1 2. they have the character of a technical brush and seem inconvenient for oral applications; PA1 3. they are very traumatic to the gums (stiffness); PA1 4. they adapt to the tooth surface only if considerable pressure is applied; PA1 5. due to the thick bristles, not all shapes can be manufactured; PA1 6. the thick bristles are hardly elastic and will break under high stress; PA1 7. they are problematic with respect to hygiene: they are too expensive for one-way use, yet they can only be sterilized but not cleaned.
In the production of dental replacements such as crowns, inlays, bridges, etc., i.e. in the field of the dental technician, similar requirements are encountered. Consequently, the above considerations also apply to grinding tools intended for this area.